Safety assessment of jumps in ski racing

Abstract

The influence of important parameters on the flight trajectory for jumps in downhill World Cup races was investigated. To quantify the impact injury risk at landing, the parameter equivalent landing height (ELH) was introduced, which considered a variable slope inclination during the landing movement. Altogether, 145 runs at four different jumps in World Cup races and trainings were recorded and analyzed. A simulation model was developed to predict the flight phase of the skier. Drag and lift areas were selected by parameter identification to fit the simulation trajectory to the two-dimensional data from the video analysis. The maximum values of the ELH which can be absorbed with muscle force was taken from the study of Minetti et al. for elite female and male ski racers. A sensitivity analysis based on the four jumps showed that ELH is mainly influenced by takeoff angle, takeoff speed, and the steepness of the landing surface. With the help of the developed simulation software, it should be possible to predict the ELH for jumps in advance. In case of an excessive ELH, improvements can be made by changing the takeoff inclination or the approach speed.

Peak ACL force during jump landing in downhill skiing is less sensitive to landing height than landing position

“…However, the importance of landing height (eLH) should not be underestimated especially in case of approaching the maximum values which a skier can absorb actively by muscle forces. Exceeding values of the eLH might result in excessive impact loads and consequently a collapse and fall of the skier 10. In this case serious injuries might result.…”

“…The present sensitivity study was based on a reference simulation tracking measurement data of a downhill skier during competition with an eLH of 1.29 m. This eLH is above an average landing height typically ranging from 0.6 m to 0.9 m 10. Therefore, extrapolation of the results of the sensitivity study (ie, trunk lean angle) is not recommended as it would result in an unrealistically high injury risk.…”

“…As a measure of landing height, the equivalent landing height (eLH) was used 10. The eLH is based on the impact velocity of the centre of mass of the skier in the direction normal to the landing surface and equals the height of a point mass with the same impact velocity on a horizontal surface.…”

“…The between-subject SD was derived from the data presented recently in Schindelwig et al 10 and amounted to 0.34 m. Based on the definition of eLH, the eLH was changed by altering the velocity component $true0v_n$ of the centre of mass of the skier model orthogonal to the snow surface at the time of initial ground contact.…”

“…Recently, Schindelwig et al 10 analysed 145 landing manoeuvres in World Cup downhill skiing. They determined the landing height of each skier and compared these values with the maximum values of the landing height which a skier can absorb actively by muscle forces.…”